"This is the final admission that Marco Rubio isn't even going to try to compete for the votes of conservatives in South Carolina or anywhere else," Cruz communications director Rick Tyler asserted in a statement.

Rubio was one of three presidential candidates, along with Cruz and Ben Carson, slated to appear at a conference. But as the event neared its conclusion, word came that Rubio could no longer make it.

Rubio communications director Alex Conant said in an email that following scheduling issues, the candidate was "running super late." The team sent surrogates Rep. Trey Gowdy and Sen. Tim Scott in Rubio's place, though they didn't end up speaking at the direction of Conservative Review.

"If he wanted to introduce Trey Gowdy and Tim Scott to speak that's perfectly fine, but that's not the way it was set up," said Mark Levin, the editor-in-chief of Conservative Review and a conservative radio host, who called it "pretty damn rude" of Rubio to miss the event.

Levin is a frequent Cruz defender and on his radio show in October called him "the most consistent conservative running." He and his publication often fiercely criticize Rubio, and some in the crowd Thursday night came in with anti-Rubio leanings, with scattered boos audible when his name was mentioned.

Rubio's campaign answered Cruz's criticisms with its own barbs, hitting the Texas Senator for his campaign's use of a photoshopped image that appeared to show Obama and Rubio shaking hands.

"Did the Cruz campaign really take a break from photoshopping pictures and recording false robocalls to send out this false press release?" Conant said in a statement. "This ridiculous attack is just the latest example of Ted Cruz's willingness to do or say anything in this campaign."

Cruz took the stage and earned a warm reception from what was clearly a friendly crowd for the Texas senator.

Levin took the stage following the senator and immediately swiped at Rubio.

"Marco Rubio, will you raise your hand?" he said. "He was supposed to be here. Probably went to McDonald's."